I am trying to power my arduino Uno and 3x Stereo 3.7W Class D Audio Amplifier - MAX98306 with a single power source. The power source is a 98watt-hour capacity 5V battery (65W max output). I broke open the batteries usb cable, and connected the red wire to the 5+ in on the arduino AND the VDD on the 3 amps, and the black wire to Gnd on everything.
when I flip the on switch, the arduino turns on, there is a hiss trough the speakers, and then a POP. Then the Arduino resets, powers up again, and then pops again; repeat forever.
interestingly, if I mess around with the common ground for the speakers, I can break this cycle, and the arduino starts running the program. So, whats going on here?
My guess is that the amps are shunting power away from the arduino, so power drops and some point during booting up. If so, is there a simple circuit i could use to delay powering the amps or the arduino, to allow each to start separately? Or do you think there might be some other problem?
Thanks, and let me know if I need to include more detail!
polymorph:
There is a Shutdown pin on that amp. Have the Arduino only enable it after the Arduino has fully booted up.
...
And probably add a lot of bypass capacitors and a large electrolytic capacitor to the 5V line.
So, should I tie the Shutdown to ground through a high R resistor (pull down resistor) to turn it off, and deliver a +5v signal from the arduino when it is booted?
And, pardon my ignorance, why are the capacitors necessary?
To keep noise (current pulses) on the 5V line from affecting all the circuits. That Class D amplifier works by PWM switching, yet has only 10uF and 0.1uF bypass (aka decoupling) capacitors.
Bottom right, C1 and C6 from Vdd to ground.
Yes, there appears to be a 10k resistor on the board to 5V (labeled 1002) so 1k should pull that line down. Or you could remove that 10k resistor and then you can use a higher value resistor like 10k or more to pull it to ground. If you use larger than 100k, I'd also place something like a 1nF or 10nF (0.01uF) capacitor across the resistor to ground.
This "5V" battery you speak of. I'm guessing its not a 5V battery, its a lithium 3.7V pack
with a boost regulator to generate 5V out at USB connector, it is probably
current limited at or near the the standard USB 0.5A current rating.
MarkT:
This "5V" battery you speak of. I'm guessing its not a 5V battery, its a lithium 3.7V pack
with a boost regulator to generate 5V out at USB connector, it is probably
current limited at or near the the standard USB 0.5A current rating.
There are no 5V batteries...
You're probably right, I didn't realize there was a difference. Its a nifty battery pack which has a USB port delivering 5v output, and a barrel connector with several cables which can output 7, 9, 12v etc. I can't remember where I bought it, and I don't have the original paperwork.
Now, to safely power the arduino through the +5v in pin, 5v input power should be 'regulated'. Do you think this pack delivers 'regulated' power. Is it still regulated if I'm delivering power to the amps as well? How can I test this?
polymorph:
Yes, there appears to be a 10k resistor on the board to 5V (labeled 1002) so 1k should pull that line down. Or you could remove that 10k resistor and then you can use a higher value resistor like 10k or more to pull it to ground. If you use larger than 100k, I'd also place something like a 1nF or 10nF (0.01uF) capacitor across the resistor to ground.
Is it better to use a higher value resistor in order to waste less power? Or is there some other reason?
rnatan:
Now, to safely power the arduino through the +5v in pin, 5v input power should be 'regulated'. Do you think this pack delivers 'regulated' power. Is it still regulated if I'm delivering power to the amps as well? How can I test this?
A multimeter - measure the voltage with no load, if its about 5.0V on DC
setting and about 0.0V on AC setting its a start...
Then try powering some (not very precious) USB device - the voltage should
stay at or close to 5.0V
Any hint of a voltage above 5.25 and its not properly regulated. 4.75V to 5.25V is
the normal tolerance range for such supplies.